Fluorine-containing elastomers having excellent flowability and being usable for molding such as injection molding can be prepared, for example, by the polymerization methods of Patent Documents 1, 2 and 3. These fluorine-containing elastomers have relatively sharp molecular weight distribution (Mw/Mn=1.8 to 3) and less branches.
On the other hand, when preparing a crosslinkable composition, shearing force is hardly applied in kneading other components, for example, a crosslinking agent and a filler, and therefore, in a short-time kneading, there is a case of causing a lack of strength.    Patent Document 1: WO 01/034666    Patent Document 2: WO 2004/009647    Patent Document 3: Examples 4 and 5 of WO 2008/001895